North Korea's nuclear weapons program has grown with each Kim regime

North Korea on Thursday announced a detailed plan to launch a volley of ballistic missiles toward the U.S. Pacific territory of Guam, a major military hub and home to U.S. bombers.

The Asian country warned that it is preparing to fire four missiles over Japan and into the waters around Guam – where some 7,000 U.S. military personnel reside among the island’s population of 160,000 American citizens.

In response, President Donald Trump turned up the heat on North Korea as tensions between the two nations grew this week. The president warned that if North Korean leader Kim Jong Un “does something in Guam, it will be an event the likes of which nobody has seen before – what will happen in North Korea.”

Trump tweeted Friday that “military solutions are now fully in place … should North Korea act unwisely.”

North Korea’s weapons program has grown exponentially over the past few decades — especially since its first leader Kim Il Sung became the catalyst for the country’s nuclear holdings. Most recently, Fox News confirmed that the East Asian country has produced a compact nuclear warhead that can be placed inside one of its advanced missiles – already believed to be capable of reaching half of the U.S.

Read on for a brief look at how North Korea’s nuclear weapons program has grown throughout the regimes.

Kim Il Sung, leader from 1948-1994

Kim Il Sung can be credited with founding North Korea and propelling the nation’s nuclear program forward — but he did not live to see his country conduct its first nuclear test.

It was under the first Kim that North Korea began to build up its nuclear reactors. And it was under his leadership that the nation began the Korean War — surely a catalyst that led the leader to believe his nation needed nuclear weapons, Dr. Sung-Yoon Lee, the Kim Koo-Korea Foundation Professor of Korean Studies at the Fletcher School at Tufts University, told Fox News in an interview.

“The seeds of nuclear aspirations were sown in the Korean War,” Lee said.

The Korean War pitted North Korea and its ally China — two nations that did not have nuclear capabilities at the time — against a nuclear-armed U.S., making it “clear to the first Kim that nuclear weapons are very powerful, a powerful deterrent,” Lee said.

Kim Jong Il, leader from 1994-2011

When the second leader of the Kim dynasty died in 2011, Kim Jong Il was remembered as the “dictator who turned North Korea into a nuclear state,” in his New York Times obituary.

And it’s Kim Jong Il that really “gets the credit of taking the country down the nuclear path,” Lee said.

In the beginning of his reign — he was North Korea’s supreme leader from 1994 to 2011 — North Korea denied that it had a nuclear weapons program.

Kim Jong Un is credited with accelerating North Korea’s push for nuclear weapons, and under the Obama administration, many of the world’s attitudes toward the East Asian nation’s nuclear capabilities became less blasé than in the past, Lee said.

And Kim Jong Un recently crossed a major threshold for his country this summer — the ability to credibly threaten the U.S. with an intercontinental ballistic missile.

North Korea’s newly demonstrated missile muscle puts Alaska within range of potential attack and stresses the Pentagon’s missile defenses like never before. It could be only a matter of time before North Korea makes an even longer-range ICBM with a nuclear warhead — putting all of the U.S. at risk.

Kim Jong Un’s acceleration of weapons tests could be because he is “more impetus” due to his young age or because “he has a lot to prove,” Lee said. But the professor contended that Kim Jong Un is “not suicidal” or “irrational,” but rather “seems to know what he’s doing.”

“If North Korea does anything in terms of even thinking about attacking anybody that we love or we represent or our allies or us, they can be very, very nervous,” Trump told reporters Thursday as fears about an attack on Guam grew.

Earlier this week, North Korea’s state media revealed a detailed plan to launch missiles toward Guam. It said the plan could be finalized within a week or so and would then go to leader Kim Jong Un for approval.